As the technology grows and advances rapidly, the battery becomes an electrical power source which is not considerably replaceable and been extensively used for devices as MP3 player, cellular phone, notebook computer, electric vehicle and the likes. Therefore, a variety of charging means for battery have been proposed, such as “Constant Trickle Current Charge”, “Constant Current Charge”, “Constant Current Constant Voltage Charge” and “Two-Step Charging”, etc.
Battery aging is known as a very important topic in battery technology. A deteriorated battery not only causes lower storage capacity and low usage efficiency, but also creates a significantly risk due to the overcharging of the cell blocks, since the terminal voltage difference of normal cell blocks is normally greater than normal cell blocks during charging operation. FIGS. 1A and 1B illustrates a schematic view of voltage distribution in accordance with a battery module having a plurality of normal and deteriorated cell blocks respectively. In FIG. 1, since all three cell blocks 101 to 103 are normal cell blocks, so the charging voltage 12.6V are equally supplied to each one of cell blocks 101 to 103, the terminal voltage of cell blocks 101 to 103 is 4.2V respectively therefore.
When deterioration that occurs in one of the cell blocks comprised in battery module 1, for example the cell block 102, the terminal voltages of cell block 102 will greater than other normal cell blocks 101 and 103 during charging. As shown in FIG. 1B, the terminal voltage of deteriorated cell block 102 is 4.3V and terminal voltages of normal cell block 101 and 103 are 4.15V respectively. Hence if cell block 102 remains deteriorated, the terminal voltage of cell block 102 would increase accordingly and may result in hazardous explosion by cell block 102.
In order to ensure the battery module fully charged, the conventional charging method typically supplies the charging voltage exceeding the safety load limit of the battery module, resulting in deteriorated scenario of the cell blocks after a long term period. Besides, though the battery module equips both over voltage protection as well as over current protection mechanisms, such mechanisms are designed for entire battery module, it is not able to reduce the risk caused by a single deteriorated cell block.
In view of the drawbacks of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally developed a charging method and device in accordance with the present invention to overcome the drawbacks of the prior art.